The invention relates to a fire extinguisher for fighting fires and nascent explosions, with a compressed gas generator and a fire extinguishing material container, as well as an initial bursting membrane closing the fire extinguishing material container with a convex surface facing the compressed gas generator, and a further bursting membrane closing the fire extinguishing material container on the exit side, the membranes having predetermined breaking points. The gas pressure of the triggered compressed gas generator causes the membrane to change over from a convex to a concave curvature in accordance with German Patent Publication DE 199 34 164.8.
For the suppression of nascent explosions, e.g. of mill dusts, coal dusts, solvent vapours and the like, containers under permanent pressure filled with fire extinguishing material (usually fire extinguishing powder) are usually used; when required, these blow the fire extinguishing material into the area where the fire is to be extinguished by means of a fast-opening valve.
A fire extinguisher whose fire extinguishing material container is closed by a flat bursting disk which opens at a relatively low overpressure of 0.1 to 1 bar is known from DE 42 24 184 A1. At least one compressed gas generator, which when triggered leads to a mixing of the fire extinguishing material with the compressed gas and sprays this mixture into the area to be protected, is connected to the fire extinguishing material container.
In the fire extinguisher in accordance with AT-E 53 948 B, a fire extinguishing material container, which is filled with liquid freon and nitrogen under high pressure, is closed by a flat bursting membrane which is torn by a detonating charge located in the immediate vicinity.
A fire extinguisher with a compressed gas generator, in which the fire extinguishing material container is closed by two flat bursting membranes, is known from DE 195 44 399 C2. The extinguishing results achieved by this fire extinguisher are only moderately good, since the bursting membranes often break open for undefined reasons.
From publication DE 199 34 164.8, the applicant knows of a fire extinguisher in which the fire extinguishing material container is closed by two spherically convex bursting membranes which are curved towards the compressed gas generator and which have an embossed predetermined breaking point. When pressure is applied, these bursting membranes indent at one point, and turn their curvature over towards the other side. In the course of this changeover from convex to concave, the membranes break almost simultaneously at the predetermined breaking points, leading to an insufficiently high pressure build-up between the compressed gas generator and the fire extinguishing material. This behaviour has an adverse effect on the spray pattern. In order to achieve an optimum spray pattern and thus good extinguishing results, however, it is necessary that the entire fire extinguishing material should be expelled uniformly.
The task of the invention in hand is to improve the described state of technology by preventing the bursting membranes from bursting simultaneously and allowing and supporting a further pressure build-up between the compressed gas generator and the fire extinguishing material.
This task is solved in accordance with the invention through Claim 1 in that in the course of the changeover of curvature, the resistance of the predetermined breaking point of the first bursting membrane is designed to be higher than the resistance of the predetermined breaking point of the further bursting membrane. In accordance with Claim 2, the resistance of the predetermined breaking point of the first bursting membrane is calculated in such a way that after the changeover in curvature has taken place, the breaking limit is only reached when the internal pressure increases further. Claim 3 establishesthat the fire extinguishing material container has two differently shaped bursting membranes.
The special advantage of the invention can be seen in that the sequence of the turning over of the curvature of both bursting membranes and the successive breaking of the predetermined breaking points is optimised in time in such a way that the fire extinguishing material is expelled from the fire extinguisher uniformly and is not asymmetrically deformed, thus leading to a fire extinguishing material distribution which is uniform in all directions.